Strong winds and heavy rain mean a risk of flooded roads. What's the correct
way to tackle standing water in your car?

The BMW's bow wave soared high over the hedgerow and you could hear the flood water clattering against the underside of the wheel arches. The driver was having a high old time, the motoring equivalent of a toddler splashing through the puddles in Wellingtons. Well he was until the engine ingested enough water to bring the car to a complete halt in the middle of the flood. I didn't stop to see what the damage was, his expression was enough to know it would be expensive.

While many cars will get through quite severe floods, there are a number of dangers. Apart from shorted-out electrics on petrol cars, there is also a risk of the engine sucking in water which, being incompressible, will cause it to lock solid (hydraulic lock), smashing connecting rods, pistons, even crankshafts. If the water is fast-moving, there is also a risk that the car could be carried off into deeper flood water with you inside.

So what should you do when you meet a flood?

First thing first, you should try to avoid it, but if you can't, you should make sure there is not more than six inches of standing water or four inches of moving water. Parking up and watching other cars and trucks negotiate the flood can be a good way of checking to see how deep it is. In particular look out for hidden dips and gullies where the water could be deeper.

If you decide to go through, stay on the crown of the road where possible and crawl through the water very slowly in first gear. Keep the engine revs up by slipping the clutch if necessary, to avoid water entering the exhaust pipe. Also avoid the temptation to make a quick exit, as going at speed can push water into the engine bay.

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Even drivers of large 4x4s should take care. Experts at Land Rover advise entering the water slowly (about 1-2mph), before acceleratin to about 3-4mph. This creates a bow wave in front of the vehicle, which will create a depression in the engine bay and keep the air intake clear of water. However, it warns that this technique won't work with beam-axled 4x4s, as the water tends to hit the front axle beam and squirt straight into the engine bay.

Avoid going too fast into even quite shallow puddles as that can lead to aquaplaning, where the tyres will no longer steer the car and you lose control. It is also inconsiderate and illegal to soak pedestrians. When you emerge from the water, dry the brakes by using them gently, and if there were leaves in the water, check the radiator matrix for blockages. Another thing to watch out for is the lunatics coming the other way. You might be observing all the best advice, but giant 4x4s or trucks racing though in the opposite direction can create such bow waves they drown your car.

If the worst happens and your car stops, leave the bonnet closed to avoid any further water ingress, climb out, lock the car and wade to dry land. In direst emergencies, you could try winding the car out by operating the starter in first or reverse gear but few starter motors will stand that sort of punishment so don't rely on it.

The AA's top tips for dealing with flooded roads

1. Only drive through water if you know how deep it is.

2. Drive slowly and steadily. Allow oncoming traffic to pass first and test your brakes as soon as you can after leaving the water.

3. Don't drive through fast-moving water, such as at a flooded bridge approach – your car could easily be swept away.

4. Driving fast through standing water is dangerous – tyres aquaplane and you lose steering control. Watch out for standing water, trying to avoid it if you can, and adjust your speed to the conditions. If you experience aquaplaning, hold the steering wheel lightly and lift off the throttle until the tyres regain grip.

5. Driving fast through standing water is inconsiderate and illegal. You could face a hefty fine and between three and nine penalty points if the police believe you were driving without reasonable consideration to other road users.

6. Driving fast through standing water can cause expensive damage – the air intake on many cars is low at the front of the engine bay and it only takes a small quantity of water sucked into the engine to cause serious damage. All engines are affected, but turbocharged petrol and diesel engines are most vulnerable.

7. As you drive slowly through standing water, keep the engine revving by slipping the clutch, otherwise water in the exhaust could stall the engine.

8. If you break down in heavy rain don't prop the bonnet open while you wait for the patrol to arrive – the engine will be more difficult to start again if the electrics are rain-soaked.